1. Field
Embodiments are directed to a technique of suppressing burn-in of an emissive element.
2. Description of the Related Art
A burn-in phenomenon arises in displays using an emissive element, such as organic light emitting diode (OLED). For example, if the same image is continuously displayed, deterioration in a pixel displaying an image with a relatively higher luminance is greater than that in a pixel displaying an image with relatively lower luminance, thereby generating a visible afterimage. This phenomenon is called “burn-in”.
To prevent burn-in, light-emitting luminance of each pixel is corrected by calculating a correction coefficient based on totalizing of luminance values of pixels. Now that display devices are used for decades, a memory capacity of about 40 through 50 bits is required for every pixel to add luminance values of all pixels over the period of use. Therefore, a mass storage device and a transfer path with a wide bandwidth capable of transferring mass data are needed due to the large number of all pixels of the display device.
To solve the above-described problem, a variety of methods are used, including the following: reducing of the size of totalizing from a pixel unit to a block unit including 4-by-4 pixels, performing totalizing every several frames, and reducing a capacity by quantization. When only a linear portion of data is compressed, quantization steps are uniform. Hence, resolution on small amplitude of a corresponding signal becomes worse when a signal with a great dynamic range is quantized.
When non-linear quantization is used, i.e., where a great quantization step is applied to great amplitude and a small quantization step is applied to small amplitude, a constant signal-to-noise ratio is obtained regardless of the amplitude size, but a quantization error becomes greater when the amplitude is great. Currently, to decrease the quantization error requires orthogonal conversion and extra transfer bandwidth and memory capacity.